nbc's liz crenshaw shows us how it works and what to look for on your bill. >> $19.95 you tend not to notice it. >> reporter: but it adds up click. he linked the mystery charges to a popular website where he said pop-up ads surface. >> you're trying to click off the darn thing and by clicking off, you're agreeing to something. >> reporter: he did not know he joined some type of subscription or membership. the charges are known as bill cramming. small unauthorized charges that appear on his statement once a month. it's more common than consumers think. >> talk to you later. >> reporter: bruce operates his own business out of his home, he noticed an unexplained $35.12 charge on his phone bill. >> i opened it up, i start making phone calls, i said, we're not paying this. they claim i signed up for some type of web service. >> reporter: when you reached this company, it said somebody in your company signed up for this? >> yes. >> reporter: could somebody in your company have signed up for this? >> not in my company. it's me. that's it. >> reporter: running a one-man show, how did this una